Audience ratings data have long occupied the attention of marketers and media managers. These are the “currencies” that support the operation of commercial media. Today, metrics can be derived from many large datasets, raising the possibility that new kinds of currencies might emerge. We argue that data on exposure are the most likely to support currencies, and that these might well go beyond traditional measures of audience size and composition. We explore the relationship between the most plausible contenders for audience currencies: size and engagement as measured by time spent. Contrary to the “Law of Double Jeopardy,” we find these metrics to be uncorrelated in an online environment, suggesting that each might have a role to play as a currency. We conclude with a discussion of how the political economy of audience measurement is likely to affect audience currencies in the age of big data.